The semiconductor industry has experienced rapid growth due to continuous improvements in the integration density of a variety of electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). For the most part, this improvement in integration density has come from repeated reductions in minimum feature size, which allows more components to be integrated into a given area. As the demand for even smaller electronic devices has grown recently, there has grown a need for smaller and more creative packaging techniques of semiconductor dies.
One such creative packaging technique is the fabrication of polymer waveguide devices. A polymer waveguide device may include a reflecting mirror portion and a wave tunnel portion formed over a substrate. The reflecting mirror may be deposited on a slope. The slope and the wave tunnel form an angle of about 45 degrees.
When a light beam strikes a 45 degree reflecting mirror, the light beam changes its direction by 90 degrees through the 45 degree reflecting mirror. The reflected light beam enters the wave tunnel and propagates along a core layer of the wave tunnel.
The reflecting mirror may be formed of a conductive material having a high reflectivity. The wave tunnel portion includes a bottom cladding layer, a core layer and an upper cladding layer. The bottom cladding layer is deposited over a portion of the reflecting mirror. The core layer may be formed of a polymer material and deposited on the bottom cladding layer by using a spin-on coating technique. The upper cladding layer is deposited over the core layer. Both the bottom cladding layer and the upper cladding layer may be formed of a polymer material.
During the fabrication process of polymer waveguide devices, due to a variety of interface stresses such as thermally induced stresses, stresses caused by the difference between hydrophilic and hydrophobic surfaces, interface peeling and delamination issues may occur at the interface between the bottom cladding layer and the reflecting mirror. The bottom cladding layer and the reflecting mirror are formed of different materials. As such, there may be poor bonding between the reflecting mirror and the bottom cladding layer. Such poor bonding may cause the waveguide device to suffer from delamination between the reflecting mirror and the bottom cladding layer.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale.